Field
The present invention relates to a tunable capacitor capable of tuning a capacitance, and more particularly to a tunable capacitor which is integrated on one semiconductor die or on one module.
Description of Related Art
In general, a radio frequency integrated circuit (RFIC) may use an impedance matching circuit for interfacing mutually different sections within an RFIC network. The impedance matching circuit improves power transfer among the sections or reduces signal reflections occurring among respective sections. For the purpose of enhancing such an impedance matching performance, a tuning matching network is employed. This is a significant issue in a circuit design.
Since parameters of various circuit elements (e.g., inductor, capacitor and the like) depend on many factors, it is difficult to accurately predict the performance of the impedance matching circuit. Therefore, a method has been used, which initially predicts the performance of the impedance matching circuit by using an on-chip circuit element for the purpose of detailed impedance matching, and then determines the validity of the circuit by measuring the result from the initial prediction. However, when the measured result is not satisfied, a new circuit element must be substituted for the circuit element. Therefore, the method is complicated and much process time-consuming. Also, there is a problem that it is difficult to physically replace a circuit element of an integrated circuit placed on a die.
Accordingly, there is a requirement for a tuning circuit capable of performs calibration or impedance matching without replacing the integrated circuit on the die. Meanwhile, in terms of noise or space, it is urgently required to develop a tunable capacitor which is implemented by a capacitor instead of an inductor and is capable of performing the calibration or impedance matching.